/*
 * Copyright 2009-2010 by The Regents of the University of California
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * you may obtain a copy of the License from
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package edu.ucr.cs.dblab.acestore.operators;

import java.nio.ByteBuffer;

import edu.ucr.cs.dblab.acestore.api.INoPrevOperatorFactory;
import edu.ucr.cs.dblab.acestore.api.IOperator;
import edu.ucr.cs.dblab.acestore.base.ACEContext;

/**
 * @author jarodwen
 * @created May 30, 2011
 */
public class IndexPageFeedOperatorFactory implements INoPrevOperatorFactory {
    
    private final int inputIdx;
    
    public IndexPageFeedOperatorFactory(int idx){
        this.inputIdx = idx;
    }

    /* (non-Javadoc)
     * @see edu.ucr.cs.dblab.acestore.api.INoPrevOperatorFactory#createOperator(edu.ucr.cs.dblab.acestore.base.ACEContext)
     */
    @Override
    public IOperator createOperator(final ACEContext ctx) {
        return new IOperator() {
            
            private int pageID;
            
            @Override
            public void open() throws Exception {
                pageID = 0;
            }
            
            @Override
            public void getNext(ByteBuffer page) throws Exception {
                if(pageID >= 0) {
                    page.position(0);
                    ByteBuffer loadPage = ctx.readPage(inputIdx, pageID);
                    System.arraycopy(loadPage.array(), 0, page.array(), 0, loadPage.capacity());
                    pageID = loadPage.getInt(loadPage.capacity() - INTSIZE - RESERVED_END);
                }
            }
            
            @Override
            public void close() throws Exception {
            }
        };
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub

    }

}
